Integrated three-leg VSC with a zig-zag transformer based three-phase four-wire DSTATCOM for power quality improvement

In this paper, a new topology of DSTATCOM (Distribution Static Compensator) is proposed for power quality improvement in a three-phase four-wire distribution system. A three-leg VSC (Voltage Source Converter) based DSTATCOM is integrated with a zig-zag transformer for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonics currents and neutral current compensation at the point of common coupling (PCC). The zig-zag transformer is used for providing a path to the zero sequence current in a three-phase four-wire distribution system. In order to reduce the voltage rating of the VSC, the zig-zag transformer is designed to have a third winding for integrating the DSTATCOM. This transformer connection provides the selection of ‘off the shelf’ VSC for this application and it also provides isolation for the power electronics system. The performance of the proposed system is validated through simulations using MATLAB software with its Simulink and Power System Blockset (PSB) toolboxes.